BIOS parameter block

In computing, the BIOS parameter block, often shortened to BPB, is a data structure in the volume boot record describing the physical layout of a data storagevolume. On partitioned devices, such as hard disks, the BPB describes the volume partition, whereas, on unpartitioned devices, such as floppy disks, it describes the entire medium. A basic BPB can appear and be used on any partition, including floppy disks where its presence is often necessary, however, certain filesystems also make use of it in describing basic filesystem structures. Filesystems making use of a BIOS parameter block include FAT12 (except for in DOS 1.x), FAT16, FAT32, HPFS, and NTFS. Due to different types of fields and the amount of data they contain, the length of the BPB is different for FAT16, FAT32, and NTFS boot sectors.[1] (A detailed discussion of the various FAT BPB versions and their entries can be found in the FAT article.) Combined with the 11-byte data structure at the very start of volume boot records immediately preceding the BPB or EBPB, this is also called FDC descriptor or extended FDC descriptor in ECMA-107 or ISO/IEC 9293 (which describes FAT as for flexible/floppy and optical disk cartridges).

de Boyne Pollard, Jonathan. "All about BIOS Parameter Blocks". Frequently Given Answers. Archived from the original on 2017-09-09. Retrieved 2016-04-18. — a description of BPBs, from version 2.0 to version 7.0

Christopher, Ken W.; Feigenbaum, Barry A.; Saliga, Shon O. (1990). "9: DOS Disk Usage". Developing applications using DOS. Wiley. ISBN0-471-52231-7. — In the "processing the BIOS parameter block" section the authors describe the evolution of the BIOS parameter block from the MS-DOS version 2.0 BPB to the PC DOS version 4.0 BPB, and label each field with the DOS version that introduced it.

Townsend, Carl (1989). "4: Disk organization and management". Advanced MS-DOS Expert Techniques for programmers. Howard M. Sams. ISBN0-672-22667-7. — Figure 4.3 contains a diagram of the version 4.0 BPB and states that the layout of BPBs "is not defined by Microsoft and can vary with different vendors". At the time that the book was written, this was true. Microsoft first publicly documented the BPB structure in the OS/2 Developers' Toolkit.

Verstak, Alex (1998-03-10). "FAT Boot Sector". Archived from the original on 2016-07-30. — Verstak reverse engineers the BIOS parameter block. The paper contains several errors. One such is its statement that "the presence of the EBPB in FAT32 is not documented by Microsoft". See:

Microsoft. "Chapter 10 - Disks and File Systems". Microsoft Windows 98 Resource Kit. Archived from the original on 2017-09-09. Retrieved 2017-09-09. — Microsoft documents a version 4.0 BPB and a new "FAT32 BIOS Parameter Block (BPB)" (a version 7.0 BPB) for DOS-Windows 98 that is "larger than a standard BPB", has an "identical structure to a standard BPB", but that also "includes several extra fields".